The M4 motorway in Port Talbot has been revealed as one of the noisiest roads in the country, according to findings.

The Welsh Government has published a series of maps to illustrate levels of noise across Wales, pinpointing the loudest areas – allowing those suffering from the constant drone of traffic or train noise to compare their decibel rating with neighbours along the busy route.

The maps show estimated levels of road traffic, railway and industrial noise in Wales’ three largest urban areas, and noise from the busiest roads and railways across the country.

The long stretch of motorway from Taibach to Baglan, in Port Talbot, is highlighted in blue – signifying noise of more than 75 decibels in a 24-hour period.

But the maps also highlight some of the "leafier" parts of Cardiff, such as Roath and Cathays, as noise hotspots – because of busy roads which run through the well-off suburbs.

Maindee, the A48 in Cardiff and Llandough also have "blue" noise corridors as a result of the busy link roads which crisscross the areas.

Roads in the centre of Cardiff, particularly around the civic centre and Cardiff Castle, are also classified as blue.

And noise levels in Morriston in Swansea and Fabian Way – the main eastern approach road to the seafront city – have also been measured at more than 75 decibels.

The maps reveal that industry and rail networks are much quieter than roads when sound levels are measured over a 24-hour period.

Baglan councillor Carol Clement, said: "I think residents who live along that stretch have probably seen an increase in traffic but there haven’t been too many complaints about the noise. I suspect it is because it because people have grown used to noise and probably try to tune it out."

Environment Minister John Griffiths said one of his top priorities is to improve the local environment for people living in our most disadvantaged areas.

He said local authorities, and other bodies, can use the maps to identify where high levels of noise coincide with other social and environmental problems.

"Noise pollution should be treated with particular seriousness when it coincides with other factors such as poor air quality, low housing standards and lack of green space," he said.

One of the maps looks at noise generated by trains. Almost all mapped railway lines are due to be electrified, and the Welsh Government is looking at the improvements in noise levels likely to result from the maps.

By calculating the noise exposure of people, making the information public, officials will be able to cut noise levels where necessary and preserve relative peace and quiet where it exists.

The Welsh Government says will shortly be consulting on a noise action plan which will bring together the noise policies and priorities of public authorities across Wales.

John Stewart, chairman of the UK Noise Association, has called for motorway speed reductions to cut noise.

He said: "These new maps more or less confirm what we know – that noise is associated with our major road routes.

"Along with aircraft noise and loud music from neighbours, road noise is the major complaint we as a campaign group get from people.

"In Wales, which only has one major airport, traffic is the major noise problem.

"One solution is modern, reduced-noise road surfacing but it is a little more expensive than traditional surfaces and requires more maintenance. There are also roadside baffle barriers but these can be ugly.

"The main solution in our view is speed reduction.

"Now the government has gone to the trouble of mapping noisy areas, perhaps it is time it took action by cutting speed limits on noisy roads."

Gloria Elliott of the Noise Abatement Society, said: "What the maps don’t show are football stadiums, nightclubs and military training ranges," he said.

"The maps need to be validated. At the moment they are just computer projections, not sound level recordings. At least they recognise there's a problem."